Catheter connectors, connector assemblies and implantable infusion devices including the same

ABSTRACT

Catheter connectors and connector assemblies that are configured to reduce the likelihood of ESC cracks.

BACKGROUND

1. Field of Inventions The present inventions relate generally toconnectors that may be used to connect a catheter to a catheter or otherdevice.

2. Description of the Related Art

Implantable infusion devices have been used to provide patients with amedication or other substance (collectively “infusible substance”) andfrequently include an implantable pump and a catheter. A reservoirstores the infusible substance within the pump and, in some instances,implantable pumps are provided with a fill port that allows thereservoir to be transcutaneously filled (and/or re-filled) with ahypodermic needle. The reservoir is coupled to a fluid transfer devicewithin the pump which is, in turn, connected to a catheter connectorthat functions as an outlet port. The catheter, which has at least oneoutlet, may be connected to a catheter connector on the pump. As such,the infusible substance may be transferred from the reservoir to thetarget body region by way of the fluid transfer device and catheter.

In some implantable infusion devices, the catheter that is locatedwithin target body region is not directly connected to the implantablepump. In the context of infusible substance delivery into thesubarachnoid space around the spinal cord or brain, the catheters tendto be relatively long, thin and soft. Some physicians are of the opinionthat, were the subarachnoid catheter to extend from the target locationto the implantable pump, the portion of the catheter that extends fromthe spine to the implantable pump would be susceptible to kinks anddamage from sutures. Accordingly, one common practice is to connect thesubarachnoid catheter to a relatively thick proximal catheter that, inturn, is connected to the implantable pump.

Many of the catheter connectors that are used to connect a catheter toan implantable pump, or to connect one catheter to another, include asupport tube that is larger in diameter than the unstretched innerdiameter of the catheter for which it is intended. The difference indiameter results in the catheter exerting a radial force on the supporttube after the catheter is pushed onto the support tube that, in turn,results in a friction force that tends to hold the catheter on thesupport tube. A barb, with a sharp edge that extends around the entirecircumference of the support tube, may also form part of the connector.The sharp edge, which is followed by a region of reduced diameter, willengage the catheter as the catheter is pulled in the removal direction.The catheter will stretch and the stretching, but for the presence ofthe support tube, would cause the catheter to “neck down,” i.e. wouldcause the inner and outer diameters of the catheter shrink. As such, theradial force exerted by the catheter increases, as will the frictionforce, in response to the catheter being pulled in the removaldirection.

The present inventor has determined that conventional barbed connectorsare susceptible to improvement. For example, the present inventor hasdetermined that a sharp edge that extends all the way around the barband support tube creates a stress riser which extends all the way aroundthe catheter at the sharp edge. The present inventor has furtherdetermined that a stress riser which extends all the way around thecatheter at the sharp edge makes the entire circumference of thecatheter at the sharp edge unnecessarily susceptible to environmentalstress corrosion (ESC) cracks.

Some barbed connectors are used in connector assemblies which alsoinclude a strain relief element that is positioned over the portion ofthe catheter associated with the barbed connector. The present inventorhas determined that conventional connector assemblies are susceptible toimprovement. For example, the present inventor has determined thatconventional connector assemblies allow cells to adhere to the outsideof the catheter at the high stress area associated with the sharp edgeof the barb. The cells excrete an acidic material that contributes toESC cracks at the sharp edge.

SUMMARY

A connector in accordance with one implementation of a present inventionincludes a support tube and a barb with one or more sharp edges that donot extend all the way around the support tube. There are a variety ofadvantages associated with such a connector. For example, the presentconfiguration provides one or more sharp-edged regions that initiate the“neck down” when the associated catheter is pulled in the removaldirection, and also provides one or more regions that are longitudinallyaligned with, and impart less stress than, the sharp-edged regions. Thecatheter regions under less stress are less likely to suffer from ESCcracks and, accordingly, will preserve the integrity of the connectionshould cracks form in the regions associated with the sharp edges.

A connector in accordance with one implementation of a present inventionincludes a support tube and a barb with first and second barb members.The first barb member includes an apex without a sharp edge and thesecond barb member include at least one sharp edge that islongitudinally spaced from the apex of the first barb member. Soconfigured, the region of the associated catheter that may besusceptible to ESC cracking will not effect the region that is formingthe seal.

A connector assembly in accordance with one implementation of a presentinvention includes a connector, with a support tube and a barb, and astrain relief element. The assembly is configured such that a seal isformed between the strain relief element and the catheter with the innersurface of the strain relief element and the outer surface of at least aportion of the catheter section over the barb. Such a seal preventscells from adhering to the portion of the catheter that is aligned withthe barb and subject to ESC cracking.

A method in accordance with one implementation of a present inventionincludes creating a seal between a strain relief element and a catheterwith the inner surface of the strain relief element and the outersurface of at least a portion of the catheter section that is over abarb. The creation of such a seal prevents cells from adhering to theportion of the catheter that is aligned with the barb and subject to ESCcracking.

The above described and many other features of the present inventionswill become apparent as the inventions become better understood byreference to the following detailed description when considered inconjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

Detailed descriptions of exemplary embodiments will be made withreference to the accompanying drawings.

FIG. 1 is a representation of an implantable infusion device having acatheter that is located within the subarachnoid space in accordancewith one embodiment of a present invention.

FIG. 2 is a section view of a catheter that is located within thesubarachnoid space.

FIG. 3 is a section view of a connector assembly in accordance with oneembodiment of a present invention.

FIG. 4 is a perspective view of a connector in accordance with oneembodiment of a present invention.

FIG. 5 is a section view taken along line 5-5 in FIG. 4.

FIG. 6 is another section view taken along line 5-5 in FIG. 4.

FIG. 7 is an enlarged side, partial section view of a catheter and aportion of the connector illustrated in FIG. 4.

FIG. 8 is a section view taken along line 8-8 in FIG. 7.

FIG. 9 is a section view taken along line 9-9 in FIG. 7.

FIG. 9A is a side view of a portion of a connector in accordance withone embodiment of a present invention.

FIG. 9B is a plan view of the connector illustrated in FIG. 9A.

FIG. 9C is a side view of a portion of a connector in accordance withone embodiment of a present invention.

FIG. 9D is a plan view of the connector illustrated in FIG. 9C.

FIG. 9E is a side view of a portion of a connector in accordance withone embodiment of a present invention.

FIG. 9F is a plan view of the connector illustrated in FIG. 9E.

FIG. 9G is a side view of a portion of a connector in accordance withone embodiment of a present invention.

FIG. 9H is a side view of a portion of a connector in accordance withone embodiment of a present invention.

FIG. 9I is a plan view of the connector illustrated in FIG. 9H.

FIG. 10 is a section view of the connector assembly illustrated in FIG.3 in a disconnected state.

FIG. 11 is a perspective view of an exemplary catheter.

FIG. 12 is a section view taken along line 12-12 in FIG. 11.

FIG. 13 is another section view taken along line 12-12 in FIG. 11.

FIG. 14 is a plan view of an implantable infusion device in accordancewith one embodiment of a present invention.

FIG. 15 is a section view of a connector assembly in accordance with oneembodiment of a present invention in a disconnected state.

FIG. 16 is a section view of the connector assembly illustrated in FIG.15 in a connected state.

FIG. 17 is an enlarged view of a portion of FIG. 16.

DETAILED DESCRIPTION OF THE EXEMPLARY EMBODIMENTS

The following is a detailed description of the best presently knownmodes of carrying out the inventions. This description is not to betaken in a limiting sense, but is made merely for the purpose ofillustrating the general principles of the inventions. The presentinventions are also not limited to use with the exemplary implantableinfusion device described herein and, instead, are applicable to otherimplantable or otherwise ambulatory infusion devices that currentlyexist or are yet to be developed.

One example of an implantable infusion device in accordance with apresent invention is generally represented by reference numeral 100 inFIG. 1. The implantable infusion device 100 includes an implantable pump102, a proximal catheter 104 that is connected to the pump, asubarachnoid catheter 106, and a connector assembly 108. The implantablepump 102 includes a housing 110. An infusible substance reservoir, afluid transfer device, control electronics and various other devices arecarried within the housing 110. Although the present inventions are notlimited to any particular type of implantable pump, exemplary pumps aredescribed in U.S. Patent Pub. Nos. 2005/0273083 and 2006/0270983, whichare incorporated herein by reference. The connector assembly 108 may beused to connect the proximal catheter 104 to the subarachnoid catheter106 before or after the subarachnoid catheter has been positioned withinthe patient's body. For example, in those instances where a stylet isused to push the distal portion of the subarachnoid catheter 106 to thetarget location, the subarachnoid catheter will be connected to theproximal catheter 104 after the stylet has been removed. The infusiblesubstance may then be delivered to, for example, the portion of thesubarachnoid space along the spine between the spinal cord SC and thearachnoid mater AM, as is illustrated in FIG. 2.

As illustrated for example in FIGS. 3-6, the exemplary connectorassembly 108 includes a connector 110, a first strain relief element 112and a second strain relief element 114. The connector 110 has first andsecond support tubes 116 and 118, first and second flanges 120 and 122,and a central portion 124. A lumen 126 extends from the free end 128 ofthe first support tube 116 to the free end 130 of the second supporttube 118. Although connectors in accordance with the present inventionsare not limited to any particular shape, the first and second supporttubes 116 and 118 and central portion 124 are generally cylindrical inshape, while the first and second flanges 120 and 122 are disk-shaped.The lumen 126 is also cylindrical in shape, but for the frusto-conicalregions associated with changes in lumen diameter. The diameter of thelumen 126 may vary as shown, may vary in other ways, or may be uniformfrom one end of the connector 110 to the other. A barb 134 is locatedbetween the flange 120 and the free end 128. The barb 134 may be anintegral part of the support tube 116 (as shown) or a separate structurethat is mounted on the support tube.

The overall shape of the exterior of the exemplary barb 134 is generallythat of a sphere and, more specifically, that of a zone of a spherewhich begins and ends where the outer surface of the barb intersects theouter surface of the support tube 116. To that end, and as illustratedin FIGS. 4-9, the exemplary barb 134 includes a first barb section 136,which gradually increases in size from outer surface 116 a of thesupport tube 116 to an apex 138, and a second barb section 140.Referring more specifically to FIGS. 7-9, the second barb section 140includes a mid-portion 142, which gradually decreases in size from theapex 138 to the outer surface 116 b, and a pair of indentations 144 and146 that extend to the apex. The second barb section mid-portion 142creates a gradual transition from the apex 138 to the outer surface 116b. The indentations 144 and 146, on the other hand, result in abrupttransitions and a pair of sharp edges 148 and 150 at the apex 138 thatare separated from one another by the mid-portion 142. So configured,the perimeter of the barb 134 that is aligned with the sharp edges 148and 150 and is perpendicular to the longitudinal axis of the supporttube 116 has regions with sharp edges and regions without sharp edges.

The exemplary first and second barb sections 136 and 140 definedifferent shapes in cross-sections taken in planes perpendicular to thelongitudinal axis of the support tube 116. Cross-sections taken inplanes perpendicular to the longitudinal axis and within the first barbsection 136 have a circular perimeter (FIG. 8). Cross-sections taken inplanes perpendicular to the longitudinal axis and within the second barbsection 140 have a non-circular perimeter and, in particular, have apair of curved perimeter portions 152 separated by a pair of flatperimeter portions 154 (FIG. 8). So configured, the first barb section136 performs the function of stretching the associated portion of thecatheter 106 into a cross-sectional shape (i.e. a circle in theillustrated embodiment) that has a perimeter, while the second barbsection 140 performs the function of stretching the associated portionof the catheter into a different cross-sectional shape (i.e. two partialcircles combined with two arcs in the illustrated embodiment) that alsohas a perimeter. The perimeters associated with each of the barbsections 136 and 140, which are measured in planes perpendicular to thelongitudinal axis, are larger on the first barb section side of the apex138 than they are on the second barb section side of the apex, whenmeasured at points along the longitudinal axis that are equidistant fromthe apex.

The exemplary barb 134 also performs the function of creating differentlevels of stress at longitudinally aligned regions of the catheter 106.As used herein, “longitudinally aligned” regions are regions that arespaced circumferentially (or are spaced about a non-circular perimeter)and also extend longitudinally along the same portion of thelongitudinal axis of the catheter. In the illustrated implementation,the regions of the catheter 106 that extend over both the first barbsection 136 and the mid-portion 142 of the second barb section 140 arenot subject to the stress concentrations associated with theindentations 144 and 146 and the sharp edges 148 and 150. The regions ofthe catheter 106 that extend over both the first barb section 136 andthe mid-portion 142 of the second barb section 140 are, therefore, underless stress than the regions of the catheter that extend over both thefirst barb section 136 and the indentations 144 and 146 of the secondbarb section 140. The regions of the catheter 106 under less stress,which are labeled LSR in FIGS. 8 and 9, will preserve the integrity ofthe connection between the catheter and the connector 110 when there arefailures at regions under greater stress, which are labeled GSR in FIGS.8 and 9. As the GSR regions deteriorate with age and stress, the LSRregions retain their strength and remain viable. These strips of LSRregion material prevent the tubing from falling off of the connectortube.

Other exemplary barbs which perform the functions described above andbelow in the context of barb 134 are generally represented by referencenumerals 134 a-134 e in FIGS. 9A-9I. Many aspects of barb 134 areincorporated into barbs 134 a-134 e and similar aspects are representedby similar reference numerals. Barbs 134 a-134 e may be incorporatedinto connectors (e.g. connector 110) and/or connector assemblies (e.g.connector assembly 108) in manner described above and below in thecontext of barb 134.

The overall shape of the exemplary barb 134 a illustrated in FIGS. 9Aand 9B is generally that of two hemispheres separated by a cylinder.More specifically, the shape includes a first zone of a sphere, whichbegins where the outer surface of the barb intersects the outer surfaceof the support tube 116 and ends at a cylinder, the cylinder itself, anda second zone of a sphere, which begins at the cylinder and ends wherethe outer surface of the barb intersects the outer surface of thesupport tube. To that end, the exemplary barb 134 a includes a firstbarb section 136, which gradually increases in size from outer surface116 a of the support tube 116 to a cylindrical section 137 a (whichdefines the apex 138 a of the barb), and a second barb section 140. Thesecond barb section 140 includes a mid-portion 142, which graduallydecreases in size from the apex 138 a to the outer surface 116 b, and apair of indentations 144 and 146 that extend to the cylindrical section137 a. The second barb section mid-portion 142 creates a gradualtransition from the cylindrical section 137 a to the outer surface 116b. The indentations 144 and 146, on the other hand, result in abrupttransitions and a pair of sharp edges 148 and 150 at the cylindricalsection 137 a that are separated from one another by the mid-portion142. So configured, the perimeter of the barb 134 a that is aligned withthe sharp edges 148 and 150 and is perpendicular to the longitudinalaxis of the support tube 116 has regions with sharp edges and regionswithout sharp edges.

The overall shape of the exemplary barb 134 b illustrated in FIGS. 9Cand 9D is generally that of a cone combined with a hemisphere. Morespecifically, the shape includes a frusto-conical portion which beginswhere the outer surface of the barb intersects the outer surface of thesupport tube 116, and a zone of a sphere which begins at thefrusto-conical portion and ends where the outer surface of the barbintersects the outer surface of the support tube. To that end, theexemplary barb 134 b includes a first barb section 136 b, which isfrusto-conical in shape and gradually increases in size from outersurface 116 a of the support tube 116 to the apex 138, and a second barbsection 140. The second barb section 140 includes a mid-portion 142,which gradually decreases in size from the apex 138 to the outer surface116 b, and a pair of indentations 144 and 146 that extend to the apex138. The second barb section mid-portion 142 creates a gradualtransition from the apex 138 to the outer surface 116 b. Theindentations 144 and 146, on the other hand, result in abrupttransitions and a pair of sharp edges 148 and 150 at the apex 138 thatare separated from one another by the mid-portion 142. So configured,the perimeter of the barb 134 b that is aligned with the sharp edges 148and 150 and is perpendicular to the longitudinal axis of the supporttube 116 has regions with sharp edges and regions without sharp edges.

The overall shape of the exemplary barb 134 c illustrated in FIGS. 9Eand 9F is generally that of a spheroid combined with a hemisphere. Morespecifically, the shape includes a zone of a spheroid which begins wherethe outer surface of the barb intersects the outer surface of thesupport tube 116, and a zone of a sphere which begins at the zone of aspheroid and ends where the outer surface of the barb intersects theouter surface of the support tube. To that end, the exemplary barb 134 cincludes a first barb section 136 c, which has a truncated spheroidshape and gradually increases in size from outer surface 116 a of thesupport tube 116 to the apex 138, and a second barb section 140. Thesecond barb section 140 includes a mid-portion 142, which graduallydecreases in size from the apex 138 to the outer surface 116 b, and apair of indentations 144 and 146 that extend to the apex 138. The secondbarb section mid-portion 142 creates a gradual transition from the apex138 to the outer surface 116 b. The indentations 144 and 146, on theother hand, result in abrupt transitions and a pair of sharp edges 148and 150 at the apex 138 that are separated from one another by themid-portion 142. So configured, the perimeter of the barb 134 c that isaligned with the sharp edges 148 and 150 and is perpendicular to thelongitudinal axis of the support tube 116 has regions with sharp edgesand regions without sharp edges.

Turning to FIG. 9G, the exemplary barb 134 d includes two barb membersthat may be contiguous or non-contiguous (as shown) and arranged suchthe region of the catheter that is aligned with the barb and is underless stress will be longitudinally spaced from the region of thecatheter that is aligned with the barb and is under greater stress. Assuch, the region of the catheter that may be susceptible to ESC crackingwill not effect the region that is forming the seal. The shape of thefirst barb member 136 d is generally that of a sphere and, morespecifically, that of a zone of a sphere which begins and ends where theouter surface of the barb intersects the outer surface of the supporttube 116. The first barb member 136 d does not include indentationsand/or sharp edges. Instead, the first barb member 136 d graduallyincreases in size from outer surface 116 a of the support tube 116 to anapex 138, and gradually decreases in size from the apex 138 to the outersurface 116 b. The first barb member 136 d is not limited to sphericalshapes and may alternatively be shaped, for example, like the barbsillustrated in FIGS. 9A-9F (albeit without the indentations). The secondbarb member 140 d gradually increases in size and defines a sharp edge148 d that extends completely around the barb member. The second barbmember 140 d is not limited to the illustrated frusto-conical shape andmay also be shaped, for example, like the barbs illustrated in FIGS. 7and 9A-9F (albeit with a sharp edge that extends all the way around thebarb). It should also be noted that the first and second barb members136 d and 140 d may be the same size (as shown) or may be differentlysized, as applications so require.

Another exemplary barb is generally represented by reference numeral 134e in FIGS. 9H and 9I. The barb 134 e extends from one end of theunderlying support tube 116 to the other, i.e. from the flange 120 tothe free end 128. The barb 134 e also includes a first barb section 136e, which has a constant cross-sectional size and shape (e.g.cylindrical) over its length, and a second barb section 140 e. Thesecond barb section 140 e includes a mid-portion 142 e, which has aconstant cross-sectional size and shape, and a pair of indentations 144and 146. The indentations 144 and 146 result in abrupt transitions and apair of sharp edges 148 and 150 at the end of the first barb section andare separated from one another by the mid-portion 142 e. So configured,the perimeter of the barb 134 e that is aligned with the sharp edges 148and 150 and is perpendicular to the longitudinal axis of the supporttube 116 has regions with sharp edges and regions without sharp edges.

Referring now to FIGS. 3 and 10, the first and second strain reliefelements 112 and 114 are flexible structures formed from materials suchas silicone rubber, polyurethane, and other soft polymeric materials,and may include protrusions 156 and 158 or other structures that enhancethe physicians ability to grip the strain relief elements during asurgical procedure. The first and second strain relief elements 112 and114 also include internal lumens 160 and 162. The internal lumens 160and 162 have relatively narrow regions 164 and 166 for the catheters 104and 106 and relatively wide regions 168 and 170 for the connectorflanges 122 and 120. The relatively wide regions 168 and 170 and theconnector flanges 122 and 120 together removably secure the first andsecond strain relief elements 112 and 114 to the connector 110.

In some instances, it may be convenient to permanently connect one ofthe catheters to a portion of the exemplary connector assembly 108. Theabdominal implantation of an infusion device, such as the exemplaryinfusion device 100 that includes a subarachnoid catheter 106 (FIG. 1),is one example of an instance where a permanent connection isconvenient. Here, the subarachnoid catheter 106 may be disconnected fromthe connector 110 so that a stylet may be temporarily positioned withinthe catheter lumen and used to push the distal portion of the catheterto the target location. There is, on the other hand, often no reason toconnect/disconnect the proximal catheter 104 and strain relief element112 from the connector 110. As such, adhesive 172 may be used topermanently connect the proximal catheter 104 to the connector 110 andstrain relief element 112 prior to the surgical procedure.

While the catheter 106 is disconnected from the connector 110 in themanner illustrated in FIG. 10, the strain relief element 114 may bepositioned distal of the proximal portion 174 of the catheter 106 sothat the catheter may be grasped by the clinician and pushed over thesupport tube 116 and barb 134 to connect the catheter to the connector110. The strain relief element 114 may then be pushed over the connectorflange 120 to secure the strain relief element to the connector.

Turning to FIGS. 11-13, and although the present connectors andconnector assemblies are not limited to use with any particular type ofcatheter, one example of a catheter that may be used in combination withthe connector assembly 108 is the exemplary subarachnoid catheter 106.The subarachnoid catheter 106 includes a catheter body 200 with a distalportion 202 and a central lumen 204 that extends from the proximal endof the catheter (i.e. the end adjacent to the connector assembly 108 inFIG. 1) to the distal end 206 of the catheter. The catheter distalportion 202 includes a plurality of exterior flow regions 208 a-c whichhave a perimeter, i.e. a circumference in the illustrated embodiment,that is smaller than that of adjacent regions of the distal portion. Aplurality of slots 210 are located between the flow regions 208 a-c, asare a plurality of protrusions 212. The distal portion 202 also includesa plurality of apertures 214 that extend from the exterior of the distalportion to the central lumen 204. So configured, cerebrospinal fluid(CSF) will be free to flow along the exterior of the catheter distalportion 202 from one flow region 208 a-c to another, as well as in andout of the apertures 214, when distal portion regions 202 a and 202 bare in contact with tissue. Such flow of CSF, which is the result of themovement of the spine and beating of the heart, dilutes medicationwithin the lumen 204 and apertures 214 that may be in contact with thearachnoid mater for prolonged periods. Thus, the configuration of thedistal portion 202 reduces the likelihood that granulomas, which may bedue to the prolonged exposure of the arachnoid mater to highconcentration drugs, will form.

In the illustrated embodiment, the apertures 214 are rectangular inshape and are located in some of the slots 210. More specifically, thereare four slots 210 and two diametrically opposed apertures 214 locatedbetween the flow regions 208 a and 208 b as well as four slots and twodiametrically opposed apertures between the flow regions 208 b and 208c. The apertures 214 between the flow regions 208 b and 208 c are offsetfrom apertures between flow regions 208 a and 208 b by ninety degrees.It should be noted here, however, that the shape, number and location ofthe apertures 214 may be varied as desired, as may the shape, number andlocation of the flow regions 208 a-c and slots 210. By way of example,but not limitation, the apertures 214 may be circular in shape and/ormay be located in the flow regions 208 a-c instead of the slots 210. Inother implementations, the flow regions and slots may be eliminated.Here, the catheter body will simply be an tubular body with apertures ofany suitable number, size and shape in the distal region.

A marker tip 216 is carried on the distal end 206 of the catheter body200. The exemplary marker tip 216 is radiopaque and, referring to FIGS.12 and 13, includes a main portion 218 and a connector 220. Theconnector 220, which is located within the central lumen 204, has aplurality of indentations 222 such as, for example, the illustratedplurality of longitudinally spaced concentric grooves. The catheterdistal portion 202 may be heated to its melting point after the markertip connector 220 has been inserted into the central lumen 204 so thatcatheter material will flow into the indentations 222. In exemplaryheating processes, hot air may be used to heat the catheter distalportion 114 and/or heat shrink tubing (e.g. polyimide or Teflon heatshrink tubing) may be positioned around the exterior of the catheterdistal portion to control the catheter shape during the melting process.A mandrel (not shown) may also be inserted into the central lumen 204proximal to the marker tip 216 prior to heating. The catheter materialwithin the indentations 222, once cooled, secures the marker tip 216 tothe catheter body 200. In other implementations, the connector may besmooth and secured to the catheter distal portion 202 with an adhesive.In still other implementations, marker tips may be configured such thatthey can be mounted on the catheter body distal end 206, and cover thedistal end of the central lumen 204, without a connector that extendsinto the central lumen.

The exemplary subarachnoid catheter 106 illustrated in FIGS. 11-13 isalso provided with an abutment 224 that is located within the centrallumen 204 proximal to the marker tip 216. The exemplary abutment 224,which is cylindrical in shape and has an outer diameter (OD) that isequal to the inner diameter (ID) of the catheter body 200, may be formedfrom any suitable material and secured to the catheter distal portion202 with an adhesive. The abutment 224 may, alternatively, be anintegral portion of the catheter body 200. Abutments may also be formedby injecting a hardenable substance (e.g. room temperature vulcanizingsilicone rubber adhesive) into the central lumen 204. The abutment 224prevents stylets from separating the marker tip 216 from the distal end206 of the catheter body 200 as the stylet is pushing the distal portion202 of the catheter 106 to a target location within, for example, thesubarachnoid space around the spinal cord.

With respect to materials, suitable materials for the connector 110include metals (e.g. titanium) and hard plastics. Suitable materials forthe catheter body 200 include, but are not limited to, polymers such aspolyurethane (e.g. Carbothane® 95A), silicone, polyethylene, andpolypropylene. Carbothane® 95A has higher tensile strength and tearresistance than, for example, silicone. As such, Carbothane® 95Afacilitates the application of greater retention forces and the use ofsharper barb edges than would be practicable with a weaker material suchas silicone, thereby reducing the likelihood of a catheter disconnect ascompared to weaker materials. Suitable materials for the marker tip 216include, but are not limited to, radiopaque materials such as platinum,gold, tungsten, barium filled plastics, and iridium.

With respect to dimensions, the dimensions of the connector 110 willdepend to some extent on the dimensions and material of the associatedcatheters. The exemplary catheter body 200, which is configured for usein the subarachnoid space, is circular in cross-section and has an OD ofabout 0.055 inches and an ID of about 0.021 inches. Here, the connectortube support 116 may have an OD of about 0.028 inches and the barb 134may have an OD at the apex 138 of about 0.044 inches. The OD of thecatheter body 200 at the exterior flow regions 208 a-c is about 0.042inches, and adjacent exterior flow regions are about 0.1 inch apart. Thepresent catheters are not, however, limited to a circularcross-sectional shape. The length of the catheter body 200 may also varyfrom about 10 inches to about 40 inches, depending on the intendedapplication.

It should be noted here that in other connector implementations, asecond barb, such as one of the exemplary barbs 134-134 e, may beassociated with a connector. In the exemplary context of connector 110,a barb may be associated with the support tube 118. Other connectors inaccordance with the present inventors may be more closely associatedwith an implantable pump or other infusion device. To that end, theexemplary infusion device 100 a illustrated in FIG. 14 includes a pump102 a, a catheter 106 and a connector 110 a with a barb 134. The pump102 a is identical to the pump 102 but for the connector 110 a.Connectors in accordance with the present inventions may also form partof adapters that allow catheters to be connected to infusion deviceswhere there is a catheter/outlet connector mismatch. One example of suchan adapter includes a connector 110 and a short catheter (or other tube)that is configured to be connected to the pump outlet connector and ismounted on the support tube 118 of the connector 110. Connectors inaccordance with the present inventions may also form part of asubcutaneous access port, such as a subcutaneous vascular access port,that includes a catheter connector.

It should also be noted here the although the connectors described abovegenerally include a pair of indentations (and an associated pair ofsharp edges), connectors in accordance with the present inventions mayalso include one, three, four or more indentations.

Other aspects of connector assemblies may be configured to reduce thelikelihood of ESC cracking. For example, connector assemblies can beconfigured so as to prevent cells, which may adhere to the catheter,excrete acidic material and contribute to ESC cracking, from beingaligned with the sharp edge of the barb where ESC cracking is mostlikely to occur. One example of such a connector assembly is generallyrepresented by reference numeral 108 a in FIGS. 15-17. Connectorassembly 108 a is substantially similar to connector assembly 108 andsimilar elements are represented by similar reference numerals.Additionally, although the exemplary connector assembly 108 a includesbarb 134, other barbs may be employed. Such barbs include, but are notlimited to, the barbs 134 a-134 e illustrated in FIGS. 9A-9I.

The exemplary connector assembly 108 a illustrated in FIGS. 15-17includes a connector 110 (with a barb 134), a first strain reliefelement 112 and a second strain relief element 114 a. The second strainrelief element 114 a has an internal lumen 162 a with a relativelynarrow region 166 a for the catheter 106 and a relatively wide region170 for the connector flange 120. The barb 134 and the relatively narrowregion 166 a are respectively sized and shaped such that the innersurface 167 a of the strain relief element 114 a (which defines theinternal lumen 162 a) will engage, at a minimum, the outer surface of aportion of the catheter 106 that is aligned with the barb when thestrain relief element is moved from the position illustrated in FIG. 15to the position illustrated in FIGS. 16 and 17. In the illustratedimplementation, the portion of the second strain relief element 114 athat is aligned with the barb 134 will be compressed and, accordingly,will form a seal 169 a (FIG. 17) with the outer surface of theassociated portion of the catheter 106. The seal 169 a will preventcells from adhering to the portion of the catheter that is aligned withthe sharp edges 148 and 150 (FIG. 7).

The diameter of the internal lumen 162 a of the second strain reliefelement 114 a in the illustrated embodiment is less than the diameter ofthe portion of the catheter that is aligned with barb apex 138 (FIG.17). Put another way, the diameter of the internal lumen 162 a is lessthan the sum of the diameter of the barb 134 at the apex 138 and twotimes the wall thickness of the catheter 106. For example, in thoseinstances where the wall thickness of the catheter is about 0.010 inchto about 0.020 inch, the diameter of the internal lumen 162 a will beless than the sum of the diameter of the barb 134 at the apex 138 plusabout 0.020-0.040 inch. In one exemplary implementation where barb 134has an OD at the apex 138 of about 0.044 inch, the diameter of theinternal lumen 162 a would be less than about 0.064 inch if the catheterwall thickness was about 0.010 inch and would be less than about 0.084inch if the catheter wall thickness was about 0.020 inch. In otherexemplary implementations, the diameter of the internal lumen 162 a maybe substantially equal to the outer diameter of the catheter 106 or theOD of the connector support tube 116. Such a configuration would createa seal between the outer surface of the catheter and the inner surfaceof the strain relief element which extends along the length of thesupport tube 116, including the portion with the barb 134.

Accordingly, one method of combining a catheter with a connectorassembly, whether at the design stage or the use stage, would entailtaking one or more of the wall thickness of the catheter, the OD of thecatheter, the OD of the support tube 116 and the OD of the barb apex 138into account. The diameter of the strain relief element internal lumen162 a and the diameter of the barb 134 at the apex 138 may be selectedas a function of catheter wall thickness. Alternatively, or in addition,in those instances where a particular catheter 106 with a given wallthickness (and/or outer diameter) is to be combined with a particularconnector 110 with a given support tube and apex diameter, the secondstrain relief element 114 a may be selected based on the diameter of itsinternal lumen 162 a in order to create the desired seal.

Although the inventions disclosed herein have been described in terms ofthe preferred embodiments above, numerous modifications and/or additionsto the above-described preferred embodiments would be readily apparentto one skilled in the art. The present inventions also includeassemblies which consist of a catheter in combination with theconnectors and connector assemblies described above and claimed below.It is intended that the scope of the present inventions extend to allsuch modifications and/or additions and that the scope of the presentinventions is limited solely by the claims set forth below.

1. A connector assembly for use with a catheter defining an outerdiameter and wall thickness, the connector assembly comprising: aconnector including a support tube, defining a longitudinal axis and anouter diameter, and a barb associated with the support tube and definingan outer diameter; and a strain relief element including an a resilientinner surface defining an internal lumen having a diameter; whereinD_(IL)≦OD_(BARB)+2(WT_(CATH)), where D_(IL) is the diameter of theinternal lumen at least at a location longitudinally aligned with thebarb when the connector, the catheter and the strain relief element arein an assembled state, OD_(BARB) is the outer diameter of the barb, andWT_(CATH) is the wall thickness of the catheter.
 2. A connector assemblyas claimed in claim 1, wherein D_(IL)<OD_(BARB)+2(WT_(CATHETER)).
 3. Aconnector assembly as claimed in claim 1, wherein D_(IL)≦OD_(S-TUBE),where OD_(S-TUBE) is the outer diameter of the support tube.
 4. Aconnector assembly as claimed in claim 1, wherein D_(IL)≈OD_(CATH),where OD_(CATH) is the outer diameter of the catheter.
 5. A connectorassembly as claimed in claim 1, wherein the barb defines a perimeter ina plane perpendicular to the longitudinal axis and includes at least onesharp edge that extends partially around the perimeter and at least oneregion without a sharp edge that extends partially around the perimeterand is longitudinally aligned with the sharp edge.
 6. A connectorassembly as claimed in claim 1, wherein the barb defines an exteriorsurface shaped like a zone of a sphere with first and secondcircumferentially spaced indentations formed therein.
 7. A method ofconnecting a catheter having an outer surface to a connector assemblythat includes a connector, with a support tube and a barb associatedwith the support tube, and a strain relief element having an innersurface, the method comprising the steps of: positioning the catheter onthe support tube such that a section of the catheter is on the barb; andcreating a seal between the strain relief element and the catheter withthe inner surface of the strain relief element and the outer surface ofat least a portion of the catheter section on the barb.
 8. A method asclaimed in claim 7, wherein the step of creating a seal includes slidingthe strain relief element over the section of the catheter that is onthe barb.
 9. A method as claimed in claim 7, wherein the connectordefines an longitudinal axis; and the step of creating a seal includescompressing a section of the inner surface of the strain relief elementthat is longitudinally aligned with the barb.
 10. A method as claimed inclaim 7, wherein the step of creating a seal further comprises creatinga seal between the strain relief element and the catheter with the innersurface of the strain relief element and the outer surface of theportion of the catheter on the support tube.
 11. A connector assembly asclaimed in claim 1, wherein the inner surface of the strain reliefelement is substantially softer than the barb.
 12. A connector assemblyas claimed in claim 1, wherein D_(IL)<OD_(BARB).
 13. An apparatus,comprising: a catheter defining an outer diameter and wall thickness; aconnector including a support tube, defining a longitudinal axis and anouter diameter, and a barb associated with the support tube and definingan outer diameter; and a strain relief element including an innersurface defining an internal lumen having a diameter; whereinD_(IL)≦OD_(BARB)+2(WT_(CATH)), where D_(IL) is the diameter of theinternal lumen at the barb when the connector, the catheter and thestrain relief element are in an assembled state, OD_(BARB) is the outerdiameter of the barb, and WT_(CATH) is the wall thickness of thecatheter.
 14. An apparatus as claimed in claim 13, whereinD_(IL)<OD_(BARB)+2(WT_(CATHETER)).
 15. An apparatus as claimed in claim13, wherein D_(IL)<OD_(S-TUBE), where OD_(S-TUBE) is the outer diameterof the support tube.
 16. An apparatus as claimed in claim 13, whereinD_(IL)≈OD_(OATH), where OD_(OATH) is the outer diameter of the catheter.17. An apparatus as claimed in claim 13, wherein the barb defines aperimeter in a plane perpendicular to the longitudinal axis and includesat least one sharp edge that extends partially around the perimeter andat least one region without a sharp edge that extends partially aroundthe perimeter and is longitudinally aligned with the sharp edge.
 18. Anapparatus as claimed in claim 13, wherein the barb defines an exteriorsurface shaped like a zone of a sphere with first and secondcircumferentially spaced indentations formed therein.